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Thanks. Looked into the Purifi that was recommended. Didn't find any readily available kits for RCA inputs, but there is a lot of discussion on the DIY and HT forums about custom builds for these. Maybe there are some solutions that I haven't found yet...

Major Contributor

Its a bit of a generalisation and myth that they are current hungry monsters . Whilst there may be a really difficult one in the range, anything I can find measurements on are really not that terrible. Any good class D amp will have no issues at all with them.

Major Contributor

Thanks. Looked into the Purifi that was recommended. Didn't find any readily available kits for RCA inputs, but there is a lot of discussion on the DIY and HT forums about custom builds for these. Maybe there are some solutions that I haven't found yet...

Best I've gathered from measurements, big Parasounds have been rated a bit conservatively, and the A21's 250/400W ratings are full-bandwidth at 0.2%. Not to go all @restorer-john here, but the Purifi's 1kHz distortion curves (ASR review) climb rapidly above 150/260W. Therefore, I conclude that the Purifi is not a good fit for someone who pushes an A21 near its limits. And I included the "unless" for the OP to consider his(?) particular needs.

Granted, it's only a couple dB difference. But a clipping Purifi is worse than an NC50x that's not overdriven, right?

Major Contributor

As does the 502 above about 350 watts. How quickly does the A21s distortion rise? The Purifi at 0.2% distortion is about 350 watts.

In any case RMS power is a poor indicator because it bears little resemblance to real world music conditions. The RMS level in music is typically only1/5th of the peak. None of these amps will run anywhere near their RMS limit with real music. Its peak thats the limitation.

However you have already hit on the major issue here. It takes massive amounts of power to seriously move the SPL levels up. An extra 100 watts makes virtually no difference.

The NC502 is only 1dB louder than the Purifi.

As mentioned the Purifi at the same rated distortion as the A21 is 350 watts. This would be 0.6dB quieter, a just perceptible difference.

Sure, nothing wrong with the NC500. At 700 watts it does provide a reasonable step up in power if you need it. It still doesnt sound quite as good as the Purifi IMO, but it depends on your requirements and speakers.

Active Member

A few thoughts as someone that has owned five pairs of Maggies over the last 25 years, from SMGas to 3.5s:

1) You don't say which Maggies. Smaller Maggies don't need as much power as larger ones.
2) Is is a common misconception that Maggies are hard to drive. Maggies are almost a purely resistive load, mostly close to 4 ohms with some models dipping to about 3 ohms. As long as the amplifier you have is comfortable driving a 4 ohm load, you are fine. The idea that they require a lot of current is pure bunk. The requirement for current is very simple: the amount needed is that which keeps the voltage from sagging into a given impedence. For example, putting 500 watts into 3 ohms requires 13 amps of current. Hardly the huge 50-100 amp current capabilities that so many amplifier companies seem fond of touting as needing to drive speakers.

So all that said, I would say the best value for your money would be recapping your A21 amp.

Last edited: Apr 9, 2020

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